Pod:
Pod is a set of closely related containers, which share PID, IPC, Network and UTS namespace. It is the basic unit of Kubernetes scheduling. The design concept of pod is to support multiple containers to share the Network and file system in one pod. The services can be combined in a simple and efficient way of inter process communication and file sharing
Disadvantages: it does not support high concurrency and high availability. When the Pod crashes, it cannot be recovered automatically
1. Create Pod
# vi pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: demo
spec:
containers:
- image: httpd
name: httpd
imagePullPolicy: Always# kubectl create -f pod.yaml
2. View Pod
# kubectl get pods
NAME READY STATUS RESTARTS AGE demo 1/1 Running 0 8d
# kubectl describe pods
3. Delete Pod
# kubectl delete pod demo
Replicaset:
While inheriting all the features of Pod, replicast can use the pre created template to define and automatically control the number of replicas. It can expand and shrink the capacity of Pod by changing the number of replicas of Pod
Disadvantages: the template template cannot be modified, so the new image version cannot be published
1. Create replicast
# vi replicaset.yaml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: demo-rc
labels:
app: demo-rc
spec:
replicas: 2
selector:
matchLabels:
app: demo-rc
template:
metadata:
labels:
app: demo-rc
spec:
containers:
- name: httpd
image: httpd
imagePullPolicy: Always# kubectl create -f replicaset.yaml
2. View replicaset
# kubectl get replicaset
NAME READY STATUS RESTARTS AGE demo-rc 1/1 Running 0 8d
# kubectl describe replicaset
3. Delete replicaset
# kubectl delete replicaset demo-rc
Deployment
While inheriting all the features of Pod and replicast, Deployment can realize real-time rolling update of template template and has the feature of our online Application life circle
1. Create Deployment
# vi deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: httpd-deployment
labels:
app: httpd-deployment
spec:
replicas: 2
selector:
matchLabels:
app: httpd-demo
template:
metadata:
labels:
app: httpd-demo
spec:
containers:
- name: httpd
image: httpd
imagePullPolicy: Always
ports:
- containerPort: 80
env:
- name: VERSION
value: "v1"# kubectl create -f deployment.yaml
2. View Deployment
# kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE httpd-deployment 2 2 2 2 8d
# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE httpd-deployment-956697567-8mqch 1/1 Running 0 8d 10.244.0.36 kube-master httpd-deployment-956697567-wcbs6 1/1 Running 0 8d 10.244.0.37 kube-master
# kubectl describe deployment
3. Update deployment
With this command, you can call out the vi editor to edit the template
# kubectl edit -f deployment.yaml
Use this command to make the current editing result effective
# kubectl apply -f deployment.yaml
Check again to see that the old version of deployment has been taken off the shelf and the new version has taken effect
# kubectl get deployment
NAME DESIRED CURRENT READY AGE httpd-deployment-6b98d94474 0 0 0 1m httpd-deployment-956697567 2 2 2 7m
4. Expansion and contraction
You can modify the assignment of replicas to expand and shrink the deployment
# kubectl scale deployment/httpd-deployment --replicas=1
5. Delete deployment
# kubectl delete deployment httpd-deployment
Lable
Label is a pair of key / value pairs from attach to Pod, which is used to pass user-defined attributes. For example, you may create a "tier" and "app" tag, mark the front-end Pod container with label (tier=frontend, app=myapp), and mark the background Pod with label (tier=backend, app=myapp). Then, you can use Selectors to select the Pod with a specific label, and let a specific Pod or Deployment use a Service to achieve a specific network configuration
Service
Service is the abstraction of application services. It provides load balancing and service discovery for applications through labels. The Pod IP and port list of matching labels form endpoints, and Kube proxy is responsible for balancing the service IP load to these endpoints. Each Service will automatically assign a cluster IP (a virtual address accessible only within the cluster) and DNS name. Other containers can access the Service through this address or DNS without knowing the operation of the back-end container.
1. Change NodePort restrictions
By default, the external NodePort limit range of Kubernetes is 30000-32767. If you want to use some common ports (80, 8080, 443), you need to enlarge this range
# vi /etc/kubernetes/manifests/kube-apiserver.yaml
Add the following node port configuration between -- service cluster IP range and secure port
... - --service-cluster-ip-range=10.96.0.0/12 - --service-node-port-range=0-32767 - --insecure-port=0 ....
Restart service
# systemctl restart kubelet
2. Create Service
# vi svc.yaml
apiVersion: v1
kind: Service
metadata:
name: demo
spec:
type: NodePort
ports:
- port: 80
nodePort: 80
selector:
app: httpd-demo# kubectl create -f svc.yaml
Tip: if you want to add an external access port to a Pod or deployment, the key value of the selector added by the service must correspond to it
3. View open ports
# kubectl get svc demo
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE demo NodePort 10.100.96.157 <none> 80:80/TCP 1h
# kubectl describe service demo
Name: demo Namespace: default Labels: <none> Annotations: <none> Selector: app=httpd-demo Type: NodePort IP: 10.100.96.157 Port: <unset> 80/TCP TargetPort: 80/TCP NodePort: <unset> 80/TCP Endpoints: 10.244.0.36:80,10.244.0.37:80 Session Affinity: None External Traffic Policy: Cluster Events: <none>